Method of encoding data

ABSTRACT

Techniques for encoding data are described herein. The method includes receiving a block payload at a physical layer to be transmitted via a data bus. The method includes establishing a block header comprising an arrangement of bits, the block header defining two block header types, wherein a hamming distance between block header types is at least four.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a Continuation Application of U.S. patentapplication Ser. No. 13/942,315, by Chen, et al., entitled “METHOD OFENCODING DATA,” filed Jul. 15, 2013, and which is incorporated herein byreference.

TECHNICAL FIELD

This disclosure relates generally to techniques for encoding data to betransmitted over a data bus. More specifically, the disclosure describesblock headers in a line code.

BACKGROUND

A line code is a coding scheme to transform a data stream into a formatsuitable for transportation on a physical media. A transmitter transmitsa line code with a source data encoded, and a receiver at a far-endrecovers the source data based on line code decoding. A host device mayconnect to a peripheral device via an interface implementing a linecoding scheme. Interfaces implementing line coding scheme may includevarious interfaces such as universal serial bus (USB), peripheralcomponent interconnect express (PCIe), DisplayPort, and the like. Oneexample of line code is 8b/10b, which transforms an 8 bit data into a 10bit line code. The 10 bit line code may subsequently be transmitted on aphysical media. A far-end receiver may deterministically recover theoriginal 8 bit data through 8b/10b line code decoding. Another exampleof line code is 64b/66b, which is constructed by prefixing a 2 bit blockheader into the original 64 bit data to form a 66 bit line code. This 66bit line code may subsequently be transmitted on a physical media. Bydecoding the 2 bit block header, a far-end receiver may recover theoriginal 64 bit data from the 66 bit line code.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram used to illustrate line code encoding at atransmission side of a physical layer.

FIG. 2 is a block diagram illustrating line code decoding at a physicallayer including a receiver.

FIG. 3 is a process flow diagram illustrating a method of aligning adata payload associated with a 4-bit block header.

FIG. 4 is a block diagram illustrating a method for establishing a blockheader.

FIG. 5 is a block diagram illustrating a method for identifying a blockheader at a receiver.

DETAILED DESCRIPTION

The subject matter disclosed herein relates to techniques for providinga header in line code. The header is a prefix indicating that a blockpayload will follow the header. The header defines the data stream ofthe block payload into a block format such that the transmitted blockpayload may be recovered. In general, two header types are definedwithin the block header including a data block header type and a controlblock header type. A data block header may indicate a data blockpayload. A control block header may indicate a control message payload.The type of header may be determined at a receiving component. In somecases, the header may contain errors. The subject matter disclosedherein comprises an arrangement of the header based on hamming distancesuch that a single-bit error may be detected and corrected, and adouble-bit error may be detected. The hamming distance of this headerarrangement is defined as the number of differences between the twoheader types at each corresponding bit position. A hamming distancebetween an arrangement for a data block header and an arrangement for acontrol block header is at least four. The hamming distance of at leastfour may enable error detection and correction as discussed in moredetail below.

As used herein, the term “header” refers to a prefix or preamble of bitsto be transmitted, or that have been transmitted, wherein the header atleast partially defines the bits that follow the header in thetransmission. In embodiments, the header described above may be a 4 bitheader in a 128 bit/132 bit (128b/132b) line coding scheme. While thedescription that follows indicates 128b/132b as an example line codingscheme, other coding schemes may be used so long as the header includesa hamming distance of at least four between the header block types.

Further, the techniques for providing a header having a hamming distanceof at least four between header block types may be implemented in aninput/output (I/O) protocol such as Universal Serial Bus (USB),peripheral component interconnect express (PCIe), DisplayPort, and thelike. The techniques described herein may also be implemented in anysuitable future I/O protocol, including a unified I/O protocol.

As discussed above, in embodiments a line code is a 128b/132b line code.A 128b/132b line code us defined with a 4 bit block header and a 128-bitblock payload. A transmitter configured to transmit 128b/132b line codemay choose which types of 132 bit blocks to transmit depending on theinformation to be transmitted. For example, if a transmitter has acontrol message to transmit, it transmits a control block with a controlblock header. If the transmitter has data to transmit, it transmits adata block with a data block header. A receiver, upon receiving a block,may decode the block header. Based on the block header type, thereceiver determines if the received block payload is a control messageor data. As discussed above, the block headers of 128b/132b line codemay be configured such that a hamming distance of four may be achievedbetween a control block header and a data block header. The hammingdistance of 128b/132b line code enables double-bit error detection andsingle-bit error detection and correction within a block header.

FIG. 1 is a block diagram used to illustrate line coding at atransmission side of a physical layer. The block diagram 100 illustratesfunctions of the physical layer of a computing device configured totransmit data with a 4-bit header, such as in 128b/132b format, whereina 4-bit header is followed by a 128-bit block payload. The physicallayer may receive a data stream including a header, as indicated by thearrow 102, payload, as indicated by the arrow 104, and a block start, asindicated by the arrow 106. The header 102 is a 4-bit header while thepayload comprises a series of sixteen 8-bit symbols. Further, the blockstart 106 may be a single bit configured to bypass a scrambler 108. Thescrambler 108 is configured to scramble the payload to be transmitted.For example, the scrambler 108 may scramble the payload such that arelatively even distribution of l's and 0's are found in the transmitteddata. The relatively even distribution provided by the scrambler enablesfor greater DC balance while providing for sufficient transition in thetransmitted payload.

The block header 102, the payload 104, and the block start 106 may beprovided to an encoder 110. The encoder 110 is to format the data usinga line code scheme. In embodiments, the encoder 110 encodes the datainto the 128b/132b format wherein the payload is 128 bits and the headeris 4 bits, such that the transmitted line data is 132 bits including theheader. As discussed above, the 4-bit header may be one of two blocktypes: a control block header or a data block header. In embodiments,when the 4-bit header is a data block header the arrangement of the4-bit header of the header is “0011,” and when the 4-bit header is acontrol block header the arrangement of the 4-bit header is “1100.”Further, the 4-bit header, due to a hamming distance of 4 between thedata block header and the control block header, enables for detectionand correction of single bit errors in the header as well as double biterror detection in the header, as discussed in more detail below inreference to FIG. 2 and FIG. 3.

In embodiments, the header may be formatted to achieve DC balance andproper transition density. Alternative criteria may apply in termsrelatively higher transition density or relatively lower transitiondensity.

As illustrated in FIG. 1, the scrambler 108 and the encoder 110 may eachreceive a core clock input configured to enable synchronization of thescrambling and encoding performed by the respective components. Theencoded data may be provided to a serializer 112 configured to convertthe transmitted payload from a parallel format to a serial format fortransmission via a transmitter differential driver 114. The encoder 110may be implemented by any suitable hardware or combination of hardwareand programming code. For example, the encoder 110 may be implemented indigital logic circuits, processors, or some combination thereof. In someembodiments, one or more components of the encoder 110 may beimplemented as a general purpose processor, such as an ASIC or FPGA,executing programming code. Accordingly, a computing device operable tocarry out the techniques described herein may include a processor and atangible, non-transitory storage medium for storing programming codeconfigured to implement the techniques disclosed herein.

FIG. 2 is a block diagram illustrating line code decoding at a physicallayer including a receiver. The receiver 202 may be a differentialreceiver with equalization configured to receive the transmitted linecode. A locally generated bit rate clock may be used in a clock recoverycircuit 204 to recover a bit rate clock embedded in the received datastream at 202. The recovered bit rate clock may be provided to a datarecovery circuit 206 and a deserializer 208. A recovered symbol clockmay be derived from the recovered bit rate clock to operate a decoder210. The deserializer 208 may convert the incoming data stream from aserial format to a parallel format and provide 8-bit bytes to thedecoder 210. In some embodiments, the decoder 210 may be a 128b/132bdecoder. The decoder 210 may be configured to work in concert withdeserializer 208 for block header alignment and recovery. The recoveredsymbol clock may enable the decoder 210 to perform the block headeralignment, block header recovery including error detection andcorrection.

In embodiments, the decoder 210 may encounter bit errors in the blockheader during the transmission. As illustrated in Table 1 below, the4-bit header of the incoming line code may have a total of 16 differentarrangements. If the data block header is set to 0011, for example, asingle-bit error, such as 0001 (second column, first row), 0010 (thirdcolumn, first row), 0111 (third column, second row), or 1011 (fourthcolumn, second row), may be encountered as a single bit error withrespect to the data block header of 0011 (fourth column and first row).Similarly, if the control block header is set to 1100, a single biterror, such as 1101 (second column, fourth row), 0100 (first column,third row), 1110 (third column, forth row), or 1000 (fourth column,third row), may be encountered as single-bit errors within respect tothe control block header of 1100 (first column, fourth row). Double biterrors of 0000 (first column, first row), 0101 (first column, secondrow), 1001 (second column, second row), 1010 (third column, third row),0110 (fourth column, third row), or 1111 (fourth column, fourth row),may be also encountered.

0000 0001 0010 0011 0101 1001 0111 1011 0100 1000 1010 0110 1100 11011110 1111

The arrangements of the data block header (0011 in the Table above) andthe control block header (1100) enable the decoder to detect thesingle-bit errors and correct the single-bit errors. Further, thearrangements illustrated in Table 1 further indicate that double-biterrors may be detected. Thus, given a hamming distance between headertypes of at least 4, single-bit errors may be detected by the decoder210 and may be corrected without requiring re-transmission of the entireblock. Error correction performed by the decoder 210 is discussed inmore detail below in reference to FIG. 3. Further, it is noted thatsingle-bit and double bit errors may be detected and reported to a linklayer associated with the physical layer 200 illustrated in FIG. 2.

The decoder 210 may recover the 4 bit header and the 128 bit payload andprovide them to an elastic buffer 212. The elastic buffer 212 mayoperate in two clock domains, one from the recovered symbol clockwriting the received data in, and one from the locally generated coreclock reading the received data out. The block payload may then beprovided to a descrambler 214. As illustrated in FIG. 2, both thedescrambler and the elastic buffer 212 receive the reference clocksignal, and the descrambler 214 may be configured to descramble theblock payload based in part on the reference clock.

FIG. 3 is a process flow diagram illustrating a method of aligning ablock payload associated with a 4-bit block header. The flow diagram 300includes at least some operations of the decoder 210 of FIG. 2. At 302,the block payload converted from serial to parallel at by thedeserializer 208 of FIG. 2 is received. The decoder 210 may determinewhether a block header has been declared at 302. If a block header isnot declared, the decoder 210 may proceed to block payload receptionbased on the symbol count 304. If the symbol count has reached 15, ablock payload is received, as indicated at 306. If the symbol count hasnot reached 15, it may proceed to the next symbol reception andincrement the symbol count accordingly as indicated at 308. Note thatthe specific number of bytes may depend on the line code definition. Forexample, in 128b/132b line code, the number of bytes of a block payloadis 16. When starting from 0, the decoder 210 may determine whether thesymbol count is 15, indicating 16 bytes in the incoming payload. If thesymbol count is equal to 15, then aligner determines that a line coding,such as 128b/132b line code, has been received at block 306. If thesymbol count is determined, at block 304, to be less than 15, then thealigner 210 may process the receive signal at block 308 and may cycleback to block 304 to determine whether the symbol count is equal to 15.

If, at block 302, a block header is declared, the decoder 210 mayproceed to block 310 wherein the block header type may be evaluated. Theevaluation at block 310 may identify the type of block headers anddetect possible errors in the block header. For example, if the blockheader is “0011,” as illustrated at block 312, the block header may beidentified at block 314 as a data block header. If the block header is“1100,” as illustrated at block 316, the block header may be identifiedat 318 as a control block header. Although in this example the datablock header is set to “0011” and the control block header is set to“1100,” other settings may be used. In embodiments, the setting of“0011” and “1100” as the data block and the control block, respectively,may enable a DC balance in the header, among other features.

Assuming that the data block header is set to “0011” and the controlblock header is set to “1100,” as illustrated in FIG. 3, the aligner 210may determine whether a header contains any single-bit errors or doublebit errors. For example, if, at block 320, the block header is any oneof the arrangements including “0001,” “0010,” “0111,” or “1011,” thedecoder 210 may detect that that the data block header reveals asingle-bit error at block 322. As another example, if, at block 324, theblock header is any one of the arrangements including “0100,” “1000,”“1101,” or “1110,” the aligner 210 may detect that the control blockheader reveals a single-bit error at block 326. In some cases, thedecoder 210 may read an arrangement, illustrated at block 328, having adouble-bit error as indicated at block 330. Both the double-bit errorsand the single-bit errors may be detectable and reported to a linklayer. However, while the single-bit errors may be corrected by thealigner 210, a double-bit error may be a fatal error as indicated atblock 332, and the link may enter a recovery process to re-establish thelink.

FIG. 4 is a block diagram illustrating a method for establishing a blockheader. At block 402, a block payload may be received at physical layer.The block payload may be configured to be transmitted via a data bus. Atblock 404, different block types may be defined by a block header. Theblock header defines at least two block header types. For example, theblock header defines a control block header and a data block header. Thedefinition of the block header types is such that a hamming distancebetween the header types is at least four.

FIG. 5 is a block diagram illustrating a method for identifying a blockheader at a receiver. The method 500 may receive, at block 502, a blockpayload at a physical layer transmitted via a data bus. A block headermay be identified at block 504. The block header defines two blockheader types, such as a control block header and a data block header.The block header is defined such that a hamming distance between the twoblock header types is at least four.

Example 1

An electronic device is described herein. The electronic device mayinclude an encoding means, such as an encoder, to establish a blockheader comprising an arrangement of bits, the block header defining atleast two block header types, wherein a hamming distance between blockheader types is at least four. The electronic device may include atransmitting means, such as a transmitter, to transmit the block headerfollowed by the block payload. An electronic device may include areceiving means, such as a receiver, to receive line encoded data; and adecoder to identify a block header comprising an arrangement of bits,the block header defining the content of a block payload, the blockheader defining two block header types, wherein a hamming distancebetween block header types is at least four.

Example 2

A method of encoding data is described herein. The method may includereceiving a block payload at a physical layer to be transmitted via adata bus. The method may include establishing a block header comprisingan arrangement of bits, the block header defining two block headertypes, wherein a hamming distance between block header types is at leastfour. Although the block header defines two header types, more than twoheader types may be defined.

Example 3

A tangible computer-readable medium comprising instructions to direct aprocessor to carry out operations is described herein. The operationsmay include receiving a block payload a physical layer transmitted via adata bus. The operations may include identifying a block headercomprising an arrangement of bits, the block header defining two blockheader types, wherein a hamming distance between block header types isat least four. The block header may be identified at a receiving means,such as at a receiver. Although the block header defines two headertypes, more than two header types may be defined.

Some embodiments may be implemented in one or a combination of hardware,firmware, and software. Some embodiments may also be implemented asinstructions stored on the tangible non-transitory machine-readablemedium, which may be read and executed by a computing platform toperform the operations described. In addition, a machine-readable mediummay include any mechanism for storing or transmitting information in aform readable by a machine, e.g., a computer. For example, amachine-readable medium may include read only memory (ROM); randomaccess memory (RAM); magnetic disk storage media; optical storage media;flash memory devices; or electrical, optical, acoustical or other formof propagated signals, e.g., carrier waves, infrared signals, digitalsignals, or the interfaces that transmit and/or receive signals, amongothers.

An embodiment is an implementation or example. Reference in thespecification to “an embodiment,” “one embodiment,” “some embodiments,”“various embodiments,” or “other embodiments” means that a particularfeature, structure, or characteristic described in connection with theembodiments is included in at least some embodiments, but notnecessarily all embodiments, of the present techniques. The variousappearances of “an embodiment,” “one embodiment,” or “some embodiments”are not necessarily all referring to the same embodiments.

Not all components, features, structures, characteristics, etc.described and illustrated herein need be included in a particularembodiment or embodiments. If the specification states a component,feature, structure, or characteristic “may”, “might”, “can” or “could”be included, for example, that particular component, feature, structure,or characteristic is not required to be included. If the specificationor claim refers to “a” or “an” element, that does not mean there is onlyone of the element. If the specification or claims refer to “anadditional” element, that does not preclude there being more than one ofthe additional element.

It is to be noted that, although some embodiments have been described inreference to particular implementations, other implementations arepossible according to some embodiments. Additionally, the arrangementand/or order of circuit elements or other features illustrated in thedrawings and/or described herein need not be arranged in the particularway illustrated and described. Many other arrangements are possibleaccording to some embodiments.

In each system shown in a figure, the elements in some cases may eachhave a same reference number or a different reference number to suggestthat the elements represented could be different and/or similar.However, an element may be flexible enough to have differentimplementations and work with some or all of the systems shown ordescribed herein. The various elements shown in the figures may be thesame or different. Which one is referred to as a first element and whichis called a second element is arbitrary.

It is to be understood that specifics in the aforementioned examples maybe used anywhere in one or more embodiments. For instance, all optionalfeatures of the computing device described above may also be implementedwith respect to either of the methods or the computer-readable mediumdescribed herein. Furthermore, although flow diagrams and/or statediagrams may have been used herein to describe embodiments, thetechniques are not limited to those diagrams or to correspondingdescriptions herein. For example, flow need not move through eachillustrated box or state or in exactly the same order as illustrated anddescribed herein.

The present techniques are not restricted to the particular detailslisted herein. Indeed, those skilled in the art having the benefit ofthis disclosure will appreciate that many other variations from theforegoing description and drawings may be made within the scope of thepresent techniques. Accordingly, it is the following claims includingany amendments thereto that define the scope of the present techniques.

1-25. (canceled)
 26. An electronic device interface, comprising: anencoder to establish a block header comprising an arrangement of bits,the block header defining two block header types, wherein a hammingdistance between the two block header types is four; and a transmitterto transmit the block header followed by a block payload, wherein a bitrate clock is to enable correction of errors in the block header withoutre-transmission of the block header and the block payload.
 27. Theelectronic device interface of claim 26, wherein the block header andblock payload are transmitted as 128b/132b line encoded data.
 28. Theelectronic device interface of claim 26, wherein the scrambler isbypassed for the bits of the block header.
 29. The electronic deviceinterface of claim 26, wherein the block payload comprises 128 bits andthe block header comprises four bits.
 30. The electronic deviceinterface of claim 26, wherein a first block header type is a data blockheader type and a second block header type is a control block headertype.
 31. The electronic device interface of claim 30, wherein the datablock header type indicates a data block payload is to follow and thecontrol block header type indicates that a control message payload is tofollow.
 32. The electronic device interface of claim 26, wherein a bitrate clock is embedded in a data stream that comprises the block headerand the block payload.
 33. The electronic device interface of claim 26,wherein in response to a configuration of a single bit, a scrambler isto be bypassed.
 34. A method of decoding data, comprising: receiving128b/132b line encoded data comprising a four-bit block header followedby a 128 bit block payload; identifying a block header comprising anarrangement of bits, the block header defining the content of a blockpayload using two block header types comprising a data block header typeand a control block header type; and wherein a hamming distance betweenthe two block header types is four.
 35. The method of claim 34, whereinthe data block header type indicates a data block payload is to followand the control block header type indicates that a control messagepayload is to follow.
 36. The method of claim 34, comprising correctinga single bit error.
 37. The method of claim 34, comprising detecting atwo bit error.
 38. The method of claim 34, wherein the four bit blockheader is not scrambled.
 39. The method of claim 34, comprisingdescrambling the block payload based in part on a reference clock. 40.The method of claim 34, comprising deriving a recovered symbol clockfrom a bit rate clock embedded in the line encoded data.
 41. The methodof claim 34, wherein the block payload is transmitted at a DisplayPort(DP) interface.
 42. A method of encoding data, comprising: establishinga block header comprising an arrangement of four bits that enablesdetection and correction of single bit errors within the block header,the block header defining two block header types; and transmitting theblock header followed by a block payload comprising 128 bits of blockdata, wherein a hamming distance between the two block header types isto enable correction of single bit errors in the block header withoutre-transmission of the block header and the block payload.
 43. Themethod of claim 42, comprising embedding the bit rate clock in a datastream that comprises the block header and the block payload.
 44. Themethod of claim 42, comprising bypassing scrambling of the bits of theblock header.
 45. The method of claim 42, comprising scrambling of thebits of the block payload.
 46. The method of claim 42, wherein the blockheader and the block payload is transmitted at a DisplayPort (DP)interface.